The present invention relates to a method and apparatus for producing a biased belt sheet having cords embedded therein which are oblique with respect to the longitudinal direction of the belt.
A vehicle tire as shown in FIG. 12, includes an annular tread A and a side wall B, a carcass ply C and a breaker D radially outwardly of the carcass ply C. The edges of the carcass ply C are turned up around bead cores E. Further, on the outside of the turned-up portions of the carcass ply C are provided. The breaker D and chafers F, as illustrated in FIG. 13, has belt plies or sheets having a number of organic or inorganic fiber cords G embedded therein. The cords lie obliquely with respect to a center line of the sheet.
A conventional method of producing a biased belt sheet is illustrated in FIGS. 9 to 11. First, a short unit sheet in the form of a parallelogram as shown in FIG. 10 is produced by cutting a rubbered belt strip in which fiber cords G are embedded in parallel to a longitudinal direction at a desired angle with respect to the longitudinal direction and at a desired length L as shown in FIG. 9. Second, unit sheets 2 are, as shown in FIG. 11, joined to one another, so as to form another belt sheet, with both the cut edges 2a ending up becoming the side edges of the new sheet. The biased belt sheet 3 thus obtained is the one in which the fiber cords G are arranged at an angle of .theta. with respect to the longitudinal direction.
In the conventional method, after being cut with a bias cutter, on a cutting conveyor, unit sheets are transferred to another conveyor by an operator or a robot, and joined one to another by manual operation.
The conventional method has the following problems: In the case of the manual operation, the operation efficiency is quite low; In the case of the use of robot, maintenance is very difficult and if the robot breaks down, the operation is forced to be suspended for a prolonged time.
In view of the above-mentioned problems, it is a main object of the present invention to provide a method and apparatus for producing a biased belt sheet which makes it possible to automatically join unit sheets, without using a robot, to simplify and facilitate the maintenance, and to eliminate manual operations to increase the productivity.